A recent development in the lighting system industry has been the introduction of light emitting diode (LED) lighting units. LED lighting units have grown in popularity because as compared traditional lighting sources such as incandescent lighting units, halogen lighting units and fluorescent lighting units, LEDs in ideal conditions are capable of outputting a larger amount of visible lumens per equivalent input power, are capable of delivering a substantially longer life time, and are capable of realizing substantial energy cost savings. However, due to external conditions involved in real world use of LED lighting units, as opposed to ideal conditions and/or laboratory conditions, it has proven difficult to realize the full benefits that LED lighting units provide over traditional lighting sources.
For example, overheating has been a recurring problem which occurs in real world environments and prevents LED lighting units from realizing their full potential. Often when an LED is exposed to too high of a temperature for too long of a time, the LED will fail prior to its reaching its rated life expectancy. As such, one of the most attractive attributes of the LED, its long life expectancy, is lost when overheating occurs. In another example, when an LED driver is exposed to too high of a temperature for too long of a time, the driver will fail prior to its reaching its life expectancy. Thus, for this additional reason, one of the most attractive attributes of LED lighting units, its long life expectancy, is again lost when overheating occurs.
Further, the overheating problem gets exacerbated in sealed lighting units because LEDs and LED drivers are themselves heat generating devices. As such, when the lighting unit is sealed, as is common in outdoor lighting units which are exposed to harsh elements such as rain, ice, and wind, the lighting unit and the components therein grow hotter and hotter as the components generate more and more heat which becomes trapped therein. As such, it has proven difficult to remedy the overheating problem in real world conditions.
As LED lighting units have evolved, the industry has attempted using secondary heat dissipating devices to lower the temperatures at and near LEDs, drivers, and other components (e.g. transformers, AC/DC converters, etc.), but secondary heat dissipating devices may be ineffective and/or cause problems of their own.
For example, some LED lighting units employ fans in an attempt to cool hot areas of the lighting unit. However, fans require additional energy to operate, add cost to the LED lighting unit, require additional space within the LED lighting unit thereby increasing the size of the ELD lighting unit, and as such add weight to the LED lighting unit. Further, fans comprise moving parts prone to mechanical failures that have proven to be frequent, which again shortens the LED lighting unit's life expectancy. Other examples are heat sinks, heat pipes, and the like. However, heat sinks, heat pipes and the like also add cost to the device, occupy a substantial amount of costly real estate within the unit, and add weight to the LED lighting unit. Adding weight and bulk to the LED lighting unit makes it cumbersome and is undesirable, especially when used for commercial purposes in difficult to reach places (e.g. 15 to 60 feet tall outdoor light poles). Other secondary heat dissipation devices include thermal gels and/or epoxies; however, gels and epoxies make it difficult to replace component parts of LED lighting units because the gels are messy and epoxies cause destruction when two affixed surfaces are decoupled from each other. Thus thermal gels and/or epoxies are undesirable because if one of the plurality of component parts of the LED lighting unit fails (e.g., one driver of a plurality of drivers), then the entire LED lighting unit has to be replaced as opposed to replacing only the failed component part of the LED lighting unit.
As such, there is a need in the lighting industry for a LED lighting fixture with new heat dissipating means which prevents the overheating of LEDs and other components but does not add substantial weight or cost to the LED lighting unit or occupy costly real estate of the lighting unit. Further, it is desirable that the heat dissipating means not involve mechanical parts. Further still, there is a need for a LED lighting fixture design that allows component parts to be repairable and replaceable in the field, in order to the save cost, size, and weight associated with the LED lighting fixture.